Sieve and strainer



June 29, 1954 J. HURST 2,682,338

SIEVE AND STRAINER Filed April 18, 1949 5 sheets-sheet 1` June 29, 1954 HURST SIEVE AND STRAINER 3 sheets-sheet 2 Filed April 18, 1949 June 29, 1954 J. HURsT SIEVE AND STRAINER 5 Sheets-Sheet 3 Filed April 18, 1949 Patented June 29,k 1954 SIEVE AND STRAINER Justin Hurst, Mayfield, England, assignor'to Russell Constructions Limited, London, England, a

British company Application April 18, 1949, Serial No. 88,189

Claims priority, application Great Britain April 21, 1948 l Claims.

This invention comprises improvements in or relating to sieves and strainers (hereinafter referred to as sieves). In prior British Patents Nos. 562,210 and 574,410 there are described sieving apparatus of the kind in which the screen is caused to move in a horizontal plane with a circular movement of small amplitude by attaching it to a rotating out-of-balance weight. The constructions described in the said patent specications comprise suspension means for the sieving member having flexibly mounted links and a frame for supporting the links such as to permit the sieving member to be presented face uppermost, above the frame and the rotating weight, in a convenient position to receive material to be sieved without any obstruction above it. The sieving elements in the aforesaid constructions were circular in shape and the sieving surface was horizontal.

It is an object of the present invention to provide a construction somewhat on the lines of the constructions described in the aforesaid patents, but which is capable of supporting large sieves in such a manner that material may be continuously supplied to them, and after treatment both the material passing through the sieve and the material retained thereby can be continuously discharged.

According to the present invention continuously operable sieving or straining mechanism comprises in combination a stationary main frame, a sieve frame adapted to support a sieve horizontally or at an angle slightly inclined to the horizontal, means for supporting the sieve frame from the main frame which are flexible and resilient and such that the sieve frame is free to move in the horizontal plane but is restrained in the vertical plane, an out-of-balance weight rotatably mounted on the sieve frame so as to rotate in or substantially in the horizontal plane, means for continuously rotating the outof-balance weight, means for feeding material to be treated on the sieve, meansbelow the sieve for collecting or passing away material which has passed through the sieve, and means for passing away over-size material which has not passed through the sieve, the combination being such that in operation a sieve may be supported by the said sieve frame and when so supported Iis given a free circular movement of small amplitude as herein defined.

Preferably the means for rotating the out-ofbalance weight is not mounted on the sieve frame but is connected to the out-of-balance weight through a flexible coupling orother flexible connection. Usually it is desirable to have the sieve slightly inclined to the horizontal and to have the means for feeding material to be treated deliver the same to the upper end of the sieve, the means for passing away oversize being at the lower end thereof.

It is found that if material to be treated whether a liquid or a solid material which is to be strained or sieved is poured onto the sieve at I the upper end thereof, the circular movement,

although it does not occur, owing to the inclination of the surface, in the same plane as the surface, assists the treatment of the material, prevents clogging and assists in the feeding of the over-size toward the discharge at the lower end ble of supporting at each end of each side frame a depending iiexibility-mounted suspension member, a sieve frame being supported on the lower ends of said suspension members and serving to support a sieve between the side frames. The sieve is preferably supported approximately at the level of the upper ends of the suspension members, the side frames being of approximately the same height so that the upper surface of the sieve is freely accessible.

The inclination of the sieve to the horizontal is preferably readily adjustable within predetermined limits.

The following is a description by way of example of one construction in accordance with the invention, from which further features of the invention will appear.

Referring to the accompanying drawings:

Figure 1 is a side elevation of the machine with certain portions shown broken away to allow the internal construction to appear;

Figure 2 is a perspective view of the whole machine;

Figure 3 is an exploded view of a flexible coupling;

Figure 4 is a detail of a flexible support for a suspension rod, and

Figure 5 is a vertical section through the drive for the out-of-balance weight.

A fixed main frame is provided consisting of two upright parallel side plates Il, I2 spaced apart by horizontal distance rods I3, Ill, I5, IE, and mounted on resilient material. Along the upper horizontal edge of each of the side plates Il, I2 there is secured a length of angle iron Il, the two angle irons extending parallel with one another and having their upper flange inturned and horizontal as shown in the drawings at E8. At the ends of the horizontal flanges i3 there mounted casing ll which contains flexible suspension means for suspension rods 23 which depend from the flanges downwardly and are connected at their lower ends by further flexible suspension means to ears 2l secured to the sides of a horizontal sub-frame 22.

As shown in Figure 4 the flexible suspension means consists of a ring 23 which is secured by screwed studs 24 and nuts 24d to the flange i8. The ring 23 is screwed externally and the casing I9 is internally screwed to i'lt on it. On the rod 20 there is a ilange 25, and above and below the flange are rubber rings 2S, 2l which are squeezed between the underside of the casing i3 and the upper face of the ring 23. The ilange the casing i9 and the ring 23 are slightly hollowed to fit the rings and the casing i9 has an upstanding hexagonal portion on which a Spanner may be iitted to enable it to be screwed down on the rubber rings. It may be locked by a bolt passing through split ears 30 formed on the outside of the casing I9 at the part where it is screwed on the ring 23.

All the suspension rods 20 should be of the same length as any inequalities may cause an undesirable secondary circular movement of the sieve frame of large amplitude and low frequency. Means should therefore be provided for adjusting the lengths of the rods 20 to avoid such undesirable movement.

The sub-frame 22 is made up of cross members which are united to a hollow longitudinal box-like or banjo member 3l and a vertical frame member 32. The vertical frame members 32 are four in number, one at each corner of the frame, and the ears 2| are secured to their lower ends while at their upper ends they extend into engagement with an adjustable sieve frame 33.

The Sieve frame 33 is or" a length comparable with the length of the horizontal angle members ll on the side frames il already referred to, and is located at approximately the same level, being narrow enough to be accommodated between the side members I'I, with room to spare sufficient to permit oi the slight desired horizontal circular movement. The sieve frame has at each corner a downwardly depending iiange 34, and the flanges 34 are bolted to the vertical corner memf bers 32 of the sub-frame by means of bolts 35. The bolts 35 pass through curved slots 36 in the members 32, and the slots 4permit adjustment of the angle of the sieve frame 33. The optimum inclination of the sieve and the length necessary to enable complete sieving to be effected depend on the nature of the material being treated. Using a mesh of 120 per inch for sieving a suspension of china clay in water I have found that an inclination of 2-3 degrees from the horizontal is satisfactory and that complete separation is effected when the oversize material has reached a distance of approximately 12 inches from the place where it is fed on to the sieve. The inclination may vary between horizontal and that shown in the drawing, which is not over The sieve frame is rectangular as viewed in plan, and a wire mesh cloth 3l is stretched across it. The cloth is tightened by means of a rectangular inner frame 3B which fits inside the sieve frame 33, and is drawn down by means of straining bolts 39 and cross bars 40. lThe use of the straining bolts 39 and cross bars 40 is similar to that usually employed for stretching cloth of a sieve and does not require further description. The

material of the sieve 31 may be wire, cloth or a bolting silk, or any other straining or sifting material. The sides of the straining frame 38 stand up around the surface of cloth 3'! and prevent material thereon from passing over the sides.

Below the sieve 31 the sieve frame 33 carries a collecting trough 45, the inclination of which is opposite to the inclination of the sieve 3l, and which at its lower end is formed with a discharge spout 46 for the throughput, that is to say for the material passing through the sieve.

At the lower end of the sieve 3l the sieve frame is extended beyond the sieve itself to afford a rectangular opening 48 through which the oversize can pass to a discharge spout 49 at the op posite ends of the machine from the spout 46 for the throughput. When inclination to the horizontal is very small, as indicated hereinabove, and still more if it is horizontal, the sides of the straining frame 38 constrain the oversize material to pass toward the outlet 48. Slightness or absence of the inclination, however, means that the oversize material will remain on the screen for a good while and has time in the case of a liquid to drain thoroughly. Any desired troughs or gutters may be arranged below the spouts 46 and 49 to collect the material and carry it away from the machine.

The box-like longitudinal member 3l of the sub-frame contains in its centre a chamber which is seen in Figure 5 of the drawing, and in which works a rotating weight 50 on a vertical spindle 5|. The spindle 5l is supported by bearings 52, 52 in the top and bottom Walls of the chamber, and the rotating weight 53 is made so that it is out-of-balance. A balance weight 53 is secured to it by a bolt 54, and the lower end of the bolt 54 works in a circumferential slot in the weight 50 so that it can be moved around the spindle 5| to any desired position. The weight is approximately in balance in the position or the parts shown in the drawing where the weight 53 is on the opposite side of the spindle from the main or solid portion of the weight 50, but if the weight 53 is moved around from this position the rotating weight as a whole becomes more and more out-of-balance. The operator can therefore adjust the degree of out-of-balance of the rotating parts, and a facilitate this adjustment the chamber is provided with a removable cover 55 by which access can be obtained to the bolt 54.

The spindle 5l passes below the member 3l and carries a disc 56 which is connected by bolts 5l, 58 (Figure 3) to a exible rubber coupling member 59, and the rubber coupling member carries other bolts 60 by which it can be connected to a disc 6l on a vertical spindle 62 running in bearings on a bracket 63 secured to the side plates I I. Below the bracket the spindle 62 carries a V- grooved pulley 64 which is connected by belt drive with a V-pulley 65 on the shaft of a motor 66 also secured to the bracket B3. The motor 66 has a vertical shaft, and although the sieve and the sub-frame each move when driven owing to the action of the out-of -balance weight, the motor and the spindle B2 do not partake of the circular movement of these parts on account of the ilexible connection afforded by the rubber ring 59. The circular movement of the sieve is small having an amplitude of approximately one quarter of an inch or less, and the speed of the spindle 5l ispreferably high, say 1500 or more revolutions per minute although this may be varied within reasonable limits by altering the size of the pulleys 64, 65.

amount of the out-of-balance weight. The exact amplitude of the movement will depend on the material being treated, but usually an amplitude lying between three sixteenths and one quarter of an inch is found suitable.

Above the sieve 31 are two parallel rods 'l0 which are supported by brackets Il from the side members Il. O-n the rods there is secured a delivery chute HI which is extended into the form of a fan shaped nozzle 12. This nozzle is directed at a low inclination towards the upper end of the sieve 31 and is adjusted so as to be close above the level of the sieve, but spaced therefrom sufliciently to allow material on the sieve to pass beneath it. The nozzle is wide enough to cover the maj or part of the Width of the sieve and it delivers material on to the sieve with the miniu mum possible shock in the opposite direction to that in which it will ow over the sieve toward the outlet 4B. The velocity of onflow is gentle and is almost immediately arrested on the sieve so that the material immediately begins to partake of the movement which is imparted to it by the circular movement of the sieve.

By the combination of parts described and claimed herein a very high throughput of material can be obtained. To obtain such a result it has been found essential to mount the sieve flexibly and resiliently in such a way that it is free to move in the horizontal plane but is restrained in the vertical plane so that in operation vertical movement is negligible or very small compared with movement in the horizontal plane. At the same time the circular movement of the sieve must be a free movement provided by the rotation of anout-of-balance weight rotatably mounted thereon or on the sieve frame so as to rotate in the horizontal plane. When in such an apparatus the Weight is rotated the sieve as a whole does not rotate but every point on the sieve surface describes a substantially circular path in the 1 horizontal plane with negligible or very small movement in the vertical plane. Such movement when the mean diameter of such circular path is small is called herein a free circular movement of small amplitude. Although the reasons for the success of the present invention in obtaining a very high throughput are not fully understood, observation of some materials during operation appears to show that the said free circular movement of smallamplitude when imparted to a sieve mounted as above described has the effect of causing the whole charge smoothly and slowly to roll and turn over soy as to bring all the fine material in turn into contact with the sieve surface. The absence of any substantial vertical movement ensured by the mounting of the sieve frame at the same time prevents bouncing of the material and consequent clogging of the sieve.

It has also been found generally desirable to mount the Whole apparatus upon resilient material for the purpose of absorbing unwanted vibrations transmitted to the main frame of the apparatus.

I claim:

1. A continuously operable sieving mechanism comprising a sieve, frame means for supporting said sieve at an angle not exceeding anangle of the order of iive degrees to the horizontal, means supporting the frame means for restraining the frame means and the sieve against movement in `6 a vertical plane but leaving the sieve free to move in a horizontal plane, rotatably mounted out-ofrbalance weight means operatively connected to the frame means and mounted to rotate in a substantially horizontal plane, means for imparting to said out-of-balance weight means circular movements in a substantially horizontal plane and of the order of not less than 1500 revolutions per minute so that said sieve is given a free vibratory circular movement at a speed of the order of not less than 1500 vibrations per minute and of an amplitude of the order of one-quarter of an inch, input means disposed adjacent one end of the sieve, and outlet means disposed adjacent the opposite end of the sieve.

2. Mechanism as claimed in claim 1 wherein the sieve-frame means comprises a sub-frame freely movable in a horizontal or substantially horizontal plane and a sieve frame for the sieve itself which sieve frame is supported on the subframe and is angularly adjustable relatively thereto.

3. Mechanism as claimed in claim 1 wherein said input means comprises nozzle means to deliver material on to the sieve, which means extend across the major part of the width of the sieve and are directed at a low inclination to- Wards the upper end of the sieve and are close to the sieve but spaced therefrom suciently to allow the material to return over the sieve beneath the nozzle means so that material is delivered on to the sieve and its velocity arrested without shock. A

4. In a sieve or strainer the combination of a stationary main frame having upstanding suspension supports spaced apart from one another, a sieve frame between said supports adapted to support a sieve with its sieving surface disposed at an angle of the order of three degrees to the horizontal, suspension rods depending from the suspension supports of the main frame into engagement with the sieve frame and resiliently connected to said supports and sieve frame, an out-of-balance weight rotatably mounted on the sieve frame and means for rotating said out-ofbalance weight at a speed of the order of 1500 revolutions per minute so that the sieve frame executes a circular movement of amplitude of approximately the order of three sixteenth of an inch, means for continuously feeding material to be treated to the upper end of said sieve, and means for separately collecting throughput and over-size material.

5l. Apparatus as claimed in claim 4 wherein the suspension rods are substantially upright, are parallel with one another, are of equal length and evenly spaced about the centre of the sieve frame so as to ensure that the circular movement of small amplitude is substantially devoid of any vertical component.

6. A straining mechanism comprising in combination a xed frame having side members vspaced apart from one another, exibly mounted straining cloth, a discharge opening -at one end of the straining cloth and means to direct liquid to be strained on to the center of the straining cloth at the other end from the discharge opening in a broad stream' in the opposite direction from the discharge opening, means for rotating the out-of-balance weight at a speedA of not less than 1500 revolutions per minuteso that the straining cloth is given a vibratory circular movement at a speed of not less than 1500 vibrations per minute and of an amplitude of the order of three-sixteenths of an inch.

7. A continuously operable sieving mechanism comprising a sieve, means for supporting said sieve at an angle of the order of' three degrees to the horizontal, means to deliver material to be treated upon the central area of` the upper end portion of the sieve and in a direction towards the upper end of the sieve, discharge means at the lower end of the sieve, and means for imparting to the sieve circular vibratory movements of the order of 1500 vibrations per minute and of the order of one-quarter of an inch in amplitude, whereby every point on the sieve surface describes a substantially circular path in the hori- 8 zontal plane so that the'material being' treated smoothly and slowly rolls andv turns' over' to bring every surface of the material into contact with the sieve surface and move the material-towards the discharge means.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 560,575 Draver May 19,1896 1,685,621 Allen Sept. 25, 1928 1,931,081 Simpson Nov. 20, 1934 2,019,547 Theobald Nov. 5, 1935 2,039,573 Weber May 4, 1936 2,149,368 Simpson Mar. 7, 1939 2,194,721 Piper Mar. 26, 1940 2,236,934 Benedict Apr. 1, 1941 2,402,340 Parmenter June'18, 1946 2,638,226 Cowan et al May 12, 1953 FOREIGN PATENTS Number Country Date 574,410 Great Britain Jan. 3, 1946 

